When Kitty Ferguson wrote her first book about Stephen Hawking in 1991, she probably did not expect to write a sequel 20 years later. The world's most recognizable cosmologist, however, has a knack for confounding expectations – not least those of his doctors, who diagnosed him with motor neurone disease nearly 50 years ago – and his contrarian spirit comes across vividly inStephen Hawking: His Life and Work. Published to honour Hawking's 70th birthday this month, Ferguson's latest chronicle of his oeuvre is somewhat more personal than its predecessors, mixing explanations of wormholes, M-theory and the anthropic principle with brief accounts of his three children, two failed marriages and hectic life as an international scientific celebrity. She has also unearthed a few genuine stunners, including an anecdote about how Hawking "found ways to use shortcuts in taking data and faked parts of the experiments" as an undergraduate at Oxford. On the whole, though, this is very much an "authorized" biography. Ferguson's tone is largely deferential, and though skirting around Hawking's second divorce seems forgivable – why interrogate someone about their domestic troubles when you could be asking their views on the universe? – the uncritical marvelling that creeps into the book's later chapters is a bit hard to take. On a brighter note, her description of Hawking's evolution as a scientific thinker is really valuable. After his pioneering work on black-hole cosmology in the 1960s and 1970s, Ferguson writes, Hawking underwent a change of heart around 1980, when he told his longtime friend and collaborator Kip Thorne that he "would rather be right than rigorous". That attitude goes some way towards explaining why Hawking has made grand claims for various unproven (and possibly unprovable) "theories of everything" over the years, and perhaps also why another friend, the physicist Leonard Susskind, once called him "the most stubborn and infuriating person in the universe". This is not, however, to dismiss Hawking's achievements. Few would dispute that he is one of the most influential physicists of his generation, and undoubtedly also one of the best at communicating big ideas to the general public. Wisely, Ferguson leaves (almost) the last word in her book to Hawking's mother Isobel, who observes that "Not all the things Stephen says probably are to be taken as gospel truth. He's a searcher, he is looking for things. And if sometimes he may talk nonsense, well, don't we all?"